dtc p0171

recently my 99 rav4 check engine light lights up. i use a scan tool to read the dtc code. it show p0171 which is a lean fuel mixture. anyone know what the most likely problem is? also sometime when i start the rav4, the engine runs likes it going to stall and sometimes it does stall. after i drove it for a minute it runs fine. i also notice when i start it the engine runs at very low rpm. any help/info will be appreciated.

I would try the following in the order given:

1. Put some injector cleaner in a tank of gas and see if that helps.
2. Remove and clean the MAF sensor
3. Check the fuel pressure (regulator) and flow (filter).
4. Check/Replace the coolant temperature sensor. <= Most Likely in your case
5. Check/Replace the HO2 (A/F ratio) sensor in front of the cat. converter (make sure you get the right part number from Toyota with your VIN).
6. Check/Replace the MAF sensor

Hi joeblack123 (http://www.automotiveforums.com/vbulletin/member.php?u=351704) ,
I have exactly the same problem with my RAV4 1998 you had desribed, appreciate to know how did you resolve that issue.
Best regards.

I have the same problem too! Please tell me how you fixed it.
Thanks,

Richard

A little info for both of you: http://www.obd-codes.com/trouble_codes/generic/p0171-system-too-lean-bank-1-oxygen-sensor.php

http://www.obd-codes.com/forums/2366-obd-codes-p0171-system-too-lean-bank-1---1999-toyota-4-runner-v6.html

thanks for the reply. The link you supplied suggests the MAF sensor to be at fault, but I made some other enquiries and apparently the 98 RAV4 doesn't have a MAF sensor. I was advised to get the fuel injectors cleaned if the CEL comes on again.

I was just about to say the same thing. Usually its caused by dirty (or even clogged) injectors. if cleaning them doesent help, id check the fuel system (filter, pump) make sure they are ok.

And no, the 96-00' RAV's didnt have MAF's, they had MAP's. that normally wouldn't be the cause of something like that, but it can happen. I'd check and make sure the vac line going to it is clean and not clogged.

Hi Richard,
appreciate to know if you have resolved the problem with your RAV
Best regards.
Fady

Finally got it fixed - it was a broken O2 sensor. However having fixed that we also had to have a tune-up as the spark plugs were really dirty.

Good luck!